So I was looking at a document on heavy water reactors, primarily to find information on the Marviken Boiling Heavy Water reactor [with a direct steam cycle based on heavy water] and stumbled upon a study of a 'self sustaining' plutonium reactor moderated with heavy water and cooled with boiling light water.
Starts about page 300 of the PDF document [in document page 285] - it is not a breeder as such, but simply recycles the plutonium in its spent fuel into a natural uranium matrix to form the replacement fuel.
It appears to require a 1.2% SEU start up load but after that can repeatedly obtain ~15GWd/t using only natural uranium makeup material.
Which is very impressive performance, even compared to the SEU-CANDU standard.
Although it obviously requires an awful lot of reprocessing - but in a constrained uranium scenario it might be worthwhile - and since burnups are so low you might be able to do cut price reprocessing by using a simple metallic fuel element and using direct fluoridation followed by distillation to obtain the plutonium fraction, which is all you want anyway. Although in that case it might be worthwhile to rectify and enrich the spent uranium as it won't have much 236U in it.

By all means go for a self sustaining plutonium reactor if feasible. I am unable to check the calculations myself.
A much more feasible method would be to use a metallic thorium blanket to simultaneously produce superior fissile U-233. It could be maximised by
irradiating but not burning the thorium in situ.
Using metallic thorium and electro-refining it in one low cost step.